Sparks CH301 Kinetic Theory of Gases Day 4 LM 09 AND HW DUE - - PowerPoint PPT Presentation

Sparks CH301 Kinetic Theory of Gases Day 4 LM 09 AND HW – DUE WEDNESDAY 8:45 AM

QUIZ: CLICKER QUESTION

• In a mixture of one mole of He and one mole
• f Ar, the partial pressure of the Ar compared

to the partial pressure of He is ? A.The same B.Higher C.Lower

POLL: CLICKER QUESTION

After reading through the question on an in-class learning activity, I typically…

A) Wait for the answer to be given then write down the correct answer. B) Start by thinking about the chemistry principles that apply then begin working on a solution. C) Begin by looking through my notes for the right formula that applies then plugging in the numbers to get an answer. D) Google the topic to find a similar problem then use that as a guide for solving this problem.

What are we going to learn today?

Understanding the Kinetic Molecular Theory Relating T, KE, and velocities of particles

• Explain the relationship between T and KE
• Explain how mass and temperature affect the

velocity of gas particles

• Recognize that in a sample of gas, particles have a

distribution of velocities

• Explain the tenets of Kinetic Molecular theory
• Apply differences in gas velocity to applications such

as diffusion and effusion

Kinetic Molecular Theory

• The particles are so small compared with the distance

between them that the volume of the individual particles can be assumed to be negligible (zero)

• The particles are in constant motion. The collisions of the

particles with the walls of the container are the cause of the pressure exerted by the gas.

• The particles are assumed to exert no forces on each other;

they are assumed to neither attract nor repel each other.

• The average kinetic energy of a collection of gas particles is

assumed to be directly proportional to the Kelvin temperature

• f the gas.

Think About Gases Microscopically What affects the average kinetic energy of a gas?

• A. Temperature
• B. Pressure
• C. Volume
• D. Temperature and Pressure
• E. Volume and Pressure

POLL: CLICKER QUESTION http://ch301.cm.utexas.edu/simulations/gas-laws/GasLawSimulator.swf

POLL: CLICKER QUESTION

In a mixture of two different gases, particles with different masses will have

• A. The same KE and the same rms velocities
• B. The same KE but different rms velocities
• C. Different KE but the same rms velocities
• D. Different KE and different rms velocities

http://ch301.cm.utexas.edu/simulations/gas-laws/GasLawSimulator.swf

DEMONSTRATION TWO VOLUNTEERS WILL SPRITZ

POLL: CLICKER QUESTION

What can we say about the velocities of the N2 gas molecules in this room?

• A. All the molecules are moving with the same absolute

velocity in the same direction.

• B. All the molecules are moving with the same absolute

velocity in random directions.

• C. The molecules are moving at a distribution of speeds

all in the same direction

• D. The molecules are moving at a distribution of speeds

in random directions.

Distribution of Velocities

The particles have a distribution of velocities

Set the T Pick molecules all going in the same direction Pick molecules all going a particular velocity

Distribution of Velocities

What does the distribution look like for different molecules at the same temperature?

This graph shows the distribution for He, Ne, Ar, and

• Xe. Which one

is He?

A B C D

POLL: CLICKER QUESTION

Distribution of Velocities

What does the distribution look like for different molecules at the same temperature?

What does the distribution look like for the same molecule at different temperatures?

A B C

POLL: CLICKER QUESTION

Which is highest temperature?

Distribution of Velocities

What does the distribution look like for the same molecule at different temperatures?

Remember the Simulator!

Temperature changes average K.E. K.E. is proportional to Temperature Proportionality constant is the Gas Constant R!

http://ch301.cm.utexas.edu/simulations/gas-laws/GasLawSimulator.swf

What is Kinetic Energy?

K.E. energy is related to mass and velocity

Who cares about velocity squared?

We think in velocity units

“root mean square” = square root of the average of the square

GROUPWORK QUIZ: CLICKER QUESTION

Rank the following from fastest to slowest in terms of rms velocity

• A. H2 at 300 K
• B. H2 at 600 K
• C. O2 at 300 K
• D. O2 at 600 K
• BADC

Use the alphanumeric response to enter the four letters in the correct order

Check on demo

Let’s think about our demo. What is the ratio

• f the speeds of the two molecules in our

demo? NH3 : HCl

Numerical Question: Give an answer to one decimal place

POLL: CLICKER QUESTION

What did we learn today?

We now know how to relate rms velocity to both temperature and mass Finally, there is a distribution of velocities. This will have huge implications for future understanding of chemistry!

DAY 4 LEARNING OUTCOMES

Explain the relationship between the kinetic energy and temperature of a gas. Explain the relationship between temperature and the velocity of a gas. Explain the relationship between molar mass and the velocity of a gas. Apply the ideas of kinetic molecular theory to a variety of gas phenomena. Describe the distribution of velocities for the particles in a gas sample and what factors affect this distribution.